JPH04292919A - Press molding method - Google Patents

Abstract

PURPOSE:To perform press molding, by a method wherein a softened resin material is put on a heat-resistant resin layer formed on a slope of a male mold and the softened resin material is placed between the male mold and female mold. CONSTITUTION:Although a softened resin material 11 to be press-molded is put on a heat-resistant resin layer 26 provided on a slope 2 of a male mold 3, since a heat-resistant resin layer 25 possesses properties making the softened resin material hard to slide, the softened resin material can be held at this position. Since holding can be performed by only unevenness-free heat-resistant resin layer like this, the title method does not become a dominant cause of a flaw to a molded body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press molding method in which a softened resin material is placed on the inclined surface of a male mold and press-molded using a female mold paired with the male mold.

0002

BACKGROUND OF THE INVENTION Conventionally, as low-pressure press molding methods, there are the following techniques. In FIG. 4, the mold 101 includes a male mold 103 having an inclined surface 102 and a female mold 107 that forms a cavity 105 together with the male mold 103. A plurality of holding pins 111 are formed on the inclined surface 102 of the male mold 103 to hold a softened resin material 109, which will be described later. To perform press molding using such a mold 101, first, as shown in FIG. Place it on top of 102. At this time, the softened resin material 109 is placed on the holding pin 111 of the inclined surface 102 so as to hang thereon. Next, the female mold 107
Press molding is performed by moving the mold body toward the male mold 103 side, and after the softened resin material is cooled and solidified, the molded body (not shown) is taken out. In this molded body, the male mold 103 side is the back surface. As described above, in conventional press molding, as a method of preventing the softened resin material from shifting on the inclined surface 102 of the male die 103, a method is adopted in which the softened resin material is hooked on the holding pin 111 formed on the inclined surface 102. ing.

0003

[Problems to be Solved by the Invention] However, when the softened resin material is held by the holding pins 111, sinks and bulges may occur not only on the back side of the molded product but also on the front surface, resulting in a defective product. In addition, if the softened resin material 109 slips and falls from the holding pin 111, the cold resin material may remain around the holding pin 111, and this remaining material cools down the next molded product partially quickly. There was also the problem of spoiling the appearance of the part. It is an object of the present invention to solve the above-mentioned problems of the conventional technology, and the object of the present invention is to prevent the softened resin material from shifting when placed on the inclined surface of the male mold, and to prevent scratches on the surface of the molded product. The purpose of the present invention is to provide a press molding method that does not cause defects.

0004

[Means for Solving the Problems] The press molding method of the present invention, which has been made to solve the above problems, uses a press that forms a molded article by sandwiching a thermoplastic softening resin material between an upper mold and a lower mold. The molding method is characterized in that a lower mold having a heat-resistant resin layer on at least a portion of the inclined surface is used, and a softened resin material is placed on the heat-resistant resin layer and press-molded.

[0005]

[Operation] In the press molding method of the present invention, a softened resin material is placed on the heat-resistant resin layer formed on the inclined surface of the lower die, and the softened resin material is sandwiched between the upper die and the lower die, and the press molding process is performed. Perform molding. In this way, the softened resin material to be press-molded is placed on the heat-resistant resin layer formed on the inclined surface of the lower die, but since the heat-resistant resin layer has the property of making the softened resin material difficult to slip, The softened resin material can be held in this position. In this way, since it can be held only by the heat-resistant resin layer without unevenness, it does not become a factor such as damage to the molded product.

[0006]

EXAMPLES In order to further clarify the structure and operation of the present invention described above, preferred examples of the present invention will be described below. In FIG. 2, the mold 1 includes a male mold (lower mold) 3 having an inclined surface 2, and a female mold (upper mold) 7 that forms a cavity 5 together with the male mold 3. A passage 9 is formed in the male mold 3 to adjust the temperature of the male mold 3 by passing hot water therethrough.

[0007] Furthermore, a plurality of holding portions 21 are formed on the inclined surface 2 of the male mold 3 along a path on which the softened resin material 11 made of polypropylene is placed. This holding part 21 is made by covering the surface and side surfaces of an iron holding block 23 with a heat-resistant resin layer 25, and is fitted into a recess 27 formed in the inclined surface 2 of the male mold 3. resin layer 25
The surface of the male mold 3 is flush with the inclined surface 2 of the male mold 3. The heat-resistant resin layer 25 is made of Teflon [(trade name, manufactured by DuPont), polytetrafluoroethylene] and has a thickness of 1.5 m.
The holding portion 21 is formed by fitting this box into a holding block 23.

To perform press molding using such a mold 1, the male mold 3 is heated to 40° C. by passing hot water through the passage 9.
Maintain at ~50°C. Next, the material supply device (not shown)
A softened resin material 11 at about 200° C. is sent out in a belt shape,
As shown in FIG. 1, it is placed on the inclined surface 2 of the male mold 3. At this time, the softened resin material 11 is placed along the path on which the heat-resistant resin layer 25 is provided. Next, press molding is performed using the male die 3 and the female die 7, and after the softened resin material 11 is cooled and solidified, a molded body (not shown) is taken out. This completes the product.

As described above, in the press molding method of this embodiment, the softened resin material 11 is placed on the heat-resistant resin layer 25 provided on the inclined surface 2 of the male mold 3 and held therein. That is, the heat-resistant resin layer 25 made of Teflon has a property of making the softened resin material 11 difficult to slip when heated by the softened resin material 11. Utilizing such properties, the heat-resistant resin layer 25 can reliably hold the softened resin material 11 even if it is a flat surface without protrusions like a conventional holding pin. Therefore, the heat-resistant resin layer 25 provided on the male mold 3 of this embodiment does not leave any scratches or the like on the surface of the molded body unlike the conventional holding pins, so there is no problem with the product. Furthermore, since the heat-resistant resin layer 25 is formed to cover the side surface of the holding block 23, when the mold etc. is opened, the heat-resistant resin layer 25 is Only the surface of the resin layer 25 will not peel off.

FIG. 3 shows a second embodiment of the present invention. That is, in the first embodiment, the heat-resistant resin layer 25 is formed in a dotted manner on the path on which the softened resin material 11 is placed, but in the second embodiment, the heat-resistant resin layer 25 is formed on the entire molding surface of the male mold 3. This is an example in which a heat-resistant resin layer 41 is formed. In addition, in order to prevent the occurrence of burrs, a heat-resistant resin layer 4 is provided on the side end portion 43 of the male mold 3.
1 is not formed. In the case of this embodiment as well, the heat-resistant resin layer 41 has a thermal conductivity of 75 W/(
Thermal conductivity is lower than 0.25W/(m・K).
It is made of Teflon. Therefore, since the heat-resistant resin layer 41 has a heat retaining effect on the softened resin material 11, the softened resin material 11 does not easily cool down. Therefore, only the portion of the softened resin material 11 that is in contact with the male mold 3 is hard to cool down between being placed on the heat-resistant resin layer 41 and press-molding, and is uniformly cooled during press-molding. Excellent moldability.

The conditions and materials applicable to the present invention may include the following as long as they have the technical functions and effects of the present invention. (1) Although polypropylene was used as the softening resin material, various other thermoplastic resins such as polyethylene, ABS, and PVC can be used. (2) Although Teflon was used as the material for the heat-resistant resin layer, other resins such as silicone resin and fluororesin may be used as long as they have excellent mold release properties. (3) The material for the heat-resistant resin layer to obtain a heat retention effect on the softened resin material has a thermal conductivity of 1.0 W/(m・K
) or less is desirable, especially 0.3W/(
m・K) is desirable. (4) When the heat-resistant resin layer is formed on the entire surface of the male mold 3 as in the second embodiment, it can be set to a predetermined thickness by overcoating. The heat retention effect of the material can be adjusted. (5) In the above example, since the lower mold is the male mold, a heat-resistant resin layer is formed on the male mold. However, when the female mold is the lower mold, a heat-resistant resin layer is formed on the inclined surface of the female mold. may be formed.

0012

[Effects of the Invention] As explained above, according to the press molding method of the present invention, a male mold having a heat-resistant resin layer formed on an inclined surface is used, and a softened resin material is placed on the heat-resistant resin layer. Therefore, the softened resin material can be held only by the heat-resistant resin layer with no unevenness, and therefore does not cause defects to the molded product. In addition, the heat-resistant resin layer has a lower thermal conductivity than the mold, so it has a heat-insulating effect on the softened resin material.
There are no product defects due to localized cold.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a male mold according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a mold according to the first embodiment.

FIG. 3 is a sectional view showing a mold according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a mold according to a conventional technique.

FIG. 5 is a perspective view showing a male mold according to a conventional technique.

[Explanation of symbols]

1 Mold 2　　　　　　　　　　　　Slope 3 Male type 5 Cavity 7 Female type 11 Softened resin material 21 Holding part 25 Heat-resistant resin layer 41 Heat-resistant resin layer

Claims (1)

[Claims] Claim 1: A press molding method in which a thermoplastic softened resin material is sandwiched between an upper mold and a lower mold to form a molded body, using a lower mold having a heat-resistant resin layer on at least a part of the inclined surface. , a press molding method characterized by placing a softened resin material on this heat-resistant resin layer and press molding it.